When Your Body Is Exposed to the Vacuum of Space, Your Blood 'Boils' And You Inflate Like A Balloon

Let's start with the obvious: once you're sucked into space, the first thing you'll notice is how cold space actually is. But while this is one of the more common understandings about the effects of space on the human body, it's not going to be the thing that kills you. 

There are plenty of other things that will do that much faster. 

Instead, it's the actual vacuum of space that causes heat to be transferred away from your body. This is going to affect your eyes, lungs, and mouth, as any water vapor will very quickly evaporate. So, rather than feeling cold in the same way one does during the winter (i.e., the air being cold, externally), the body has no air or water to insulate it, which results in your eventual freezing.  

Today, if you were to walk outside and spend a few hours in the sun, you may end up with a bad sunburn. In which case, throw some aloe on, give it a few days of gingerly putting clothes back on, and you'll be okay. The reason? The Earth's atmosphere protects us from the sun's ultraviolet rays, and keeps radiation down to a minimum. 

But if you happen to be floating in space? Well, say goodbye to that protective shield, because out here, your skin is going to burn very quickly, resulting in skin cancer in only a matter of seconds from the intense radiation.

And while we're on the topic of how dangerous the sun is out here, the same rule applies in space as it does on Earth: don't stare directly into it. 

While on the ground it would take roughly about a minute-and-a-half to get serious eye damage (in what is called "solar retinopathy"), up in space, that time span is significantly shortened, and one could easily go blind by staring directly into it for even a brief amount of time. 

By now, it's a little bit chilly, you have a pretty bad sunburn, it's possible you've already gone blind, and, on top of all other things, you're still drifting away in the crippling loneliness of space. 

Things could be better, but, unfortunately, they're going to get a lot worse. 

In this case, what is called ebullism is going to set in. And the process of ebullism is relatively simple: in everyone's blood, there is nitrogen. And as that nitrogen dissolves as a result of space's vacuum, it will begin to form bubbles -- LOTS of bubbles. So much so, in fact, that they're all going to expand, starting at your extremities, until your body gradually begins to physically expand as a result. 

Just like the vacuum's effects on your skin, your brain is also going to run into some serious trouble when it's deprived of all the lovely comforts of a stable atmosphere and regulated air pressure. 

How so, exactly? Well, remember how the liquid from your body is going to be quickly sucked out? And how its gasses are going to form bubbles that force you to expand? A similar reaction is going to go down inside your skull -- as in, all the oxygen that was helping you breathe and stay conscious is now going to disappear.

And after about 15 seconds? You're going to pass out, with no way to save yourself. 

And if having your brain slowly die out isn't bad enough, you're going to slowly lose the air in your lungs due to space's vacuum as well. Similarly to how scuba divers experience "the bends", there is going to be a strong buildup of atmospheric pressure happening inside your lungs if there's ANY air left in them. 

As a result, say goodbye to your lungs - they're about to completely rupture under pressure.